The present invention relates to a percussion mechanism for a repetitively hammering hand power tool—preferably a drill hammer and/or percussion hammer—that has a striker which can move axially forward and backward in a guide barrel, and having a device that exerts pressure on the striker, by which the striker can be set into a forward motion in the direction of a tool bit that can be inserted into the hand power tool.
One such compression percussion mechanism that executes repetitive striking motions for an electropneumatic drill hammer and/or percussion hammer, as is taught by German Patent DE 198 10 088 C1, comprises an eccentric drive, a piston, and a striker. With these three elements, a rotary motion is converted into a reciprocating motion. The axial forward and backward motion of the striker in a guide barrel happens in the following way:
The piston moved in the forward direction by the eccentric drive compresses the air cushion between the piston and the striker, causing the striker to shoot freely onto the tool bit inserted into the power tool. The striker transfers its percussion energy to the tool bit and there receives a pulse in the reverse direction. Simultaneously, the piston is likewise moved backward by the eccentric drive, creating a certain underpressure in the air cushion between the piston and the striker. As soon as the piston has reached its turning point and the striker shoots still farther against the piston, the air cushion between the two is compressed, resulting in compression, with the consequence that upon the next forward motion of the piston, the striker shoots forward against the tool bit at an even higher speed.
A compression percussion mechanism of this kind is technically relatively complex, since besides the striker that moves in the axial direction it requires an eccentric drive with a piston that is likewise displaceable in the axial direction. A mutually independent adjustment of the striking frequency and the striking intensity is not possible in a compression percussion mechanism of this kind.